1. Technical Field
The present invention relates to a light source unit and image projection apparatus to emit light to a target.
2. Background Art
Screen images of personal computers, video images, and image data stored in memory cards can be transmitted to image projection apparatuses known as projectors that can project images onto a screen. In the projector, light emitted from a light source is focused on a micro mirror display device known as a digital micro mirror device (DMD), or a liquid crystal plate, to form images, which are then displayed as projection images such as color images on the screen.
In the projector, a high intensity discharge lamp has been conventionally used as the light source, but other light sources are recently developed. For example, semiconductor elements such as a light emitting diode (LED), a laser diode (LD), or organic electroluminescence (OEL) have been developed as the light source. The laser diode can be used as the light source for the image projection apparatuses to enhance, for example, color reproduction performance, light emission efficiency, and light use efficiency. Further, because the laser diode is a point light source or projects parallel beams, a lighting system can be designed easily, color lights can be synthesized using a simple configuration, and a projection lens having a small numerical aperture (NA) can be used.
When the light emitting element such as the laser diode (LD) is employed as the light source for the image projection apparatuses, light quantity of one single light emitting element is not enough for light quantity required for the image projection apparatuses.
In view of such issue, a semiconductor light source apparatus of JP-2011-197593-A is devised, in which a number of light emitting elements are packed two dimensionally on a plane, and light quantity required for an image projection apparatus can be obtained by adding light quantity of the number of light emitting elements. In this semiconductor light source apparatus, a number of light emitting elements are supported by a light emitting element supporter in a matrix pattern while setting the light axis of each of semiconductor light emitting elements to be substantially parallel to each other. Light emitted from the semiconductor light emitting elements are condensed by using a collimator lens retained at a lens holder of each of the semiconductor light emitting elements to obtain light quantity required for the image projection apparatus.
As for image projection apparatuses using a light emitting element assembly arranging a number of light emitting elements with a dispersed pattern on two dimensional direction as a light source, efficient cooling of the light emitting elements becomes an issue because if the cooling is not enough, light emitting quantity may not be stabilized, and lifetime of the light emitting elements becomes short.
The light emitting element assembly can be cooled by disposing a heat dissipater such as a heat sink on a rear side of a light emitting element supporter that supports the light emitting element assembly, in which air is supplied to the heat dissipater to cool the light emitting element assembly using a cooling fan.
However, cooling effect may not be enough just by cooling the rear side of the light emitting element supporter. Especially, when a large number of light emitting elements are densely disposed on a plane to achieve a small-sized light source, or when a large number of light emitting elements are used to increase light quantity, cooling effect may not be enough.